my crepe myrtles are blooming ,but the blooms are turning brown immediately. soil is slightly moist, fertilized a month ago. I`ve been using the same fertilizer for years. Temperature in the 90`s, not unusual for Fresno .

Welcome to NGA, chokus. Wow, that is rare for the blooms to die so quickly if the trees are not under stress. I would expect an environmental problem like an extreme lack of water or weather issues. Let me ask you some general questions and sorry they are so many.

How old and how tall are the CMs?

You said you were watering. How much and how deeply? The amount of water needed to appropriately water a crape myrtle varies based on the size of the tree and the type of soil. But a general rule on established CMs is to moisten the top 12-24 inches of soil. Does that sound about what you are doing?

How quick are the blooms browning when you said "immediately"? The cluster of flowers usually opens in stages and may take a few days (?) to fully open. Do they partially open and brown out overnight every night? How cold are your overnight temperatures?

Have you removed a cluster of browned flowers to look for fungal problems and insects (you may need a magnifying lens)? No sooty mold, spider mites or aphids even from last year?

Are the trees planted in full sun? Are they planted under other larger trees? Do they have any plants growing under them which may compete for nutrients and water?

What fertilizer are you using (name)? What is its NPK Ratio and how much does the product label say that you should use? Are you using that amount or exceeding it?

What kind of soil do you have? Any nutrient issues with the soil (sandy soils for example tend to lack many nutrients)? Have you done a formal soil test? Any pests causing issues to roots of CMs or other plants?

Again, sorry for all the questions....

CM`S about 10 years old. stand 6` high and 8` wide. well established and look healthy.Soil is sandy loam. Drip feed about 8 gallons twice aweek.They bloom a purple flower , then within a day flowers turn brown. temperatures are in the 50`s at night and 90`s during the day . Trees shade in the A.M. then about noon full sunlight. Can`t see any bugs or mold using a magnifying glass. NO weeds or other growth at least 6` away. Last soil sample showed slightly Alkaline( 7.2). Fertilizer-MIRACLE GRO bloom buster-10-52-10.About every 30 days mixed in a 1 1/2 gallon jug and poured on the roots. NO weed killer used anywhere near plants.

You are fertilizing too much but I don't think that that is the problem.
My opinion, you may have thrips or aphids.

Have you removed a cluster of browned flowers to look for fungal problems and insects (you may need a magnifying lens)? No sooty mold, spider mites or aphids even from last year?

Any pests causing issues to roots of CMs or other plants?

I am in Florida zone 9 and do not fertilize my crape myrtles at all or water too much. They are in full sun. However, I think you may have a problem with fertilizing too often.

label on fertilizer says every 7to
14 days. I fertilize usually 30 to 45 days. Once the 100 degree day's start, no more fertilizing until new spring growth starts.

Let me respond this way.
If their label says fertilize every two weeks versus every six weeks or two months, which makes them more money???

The danger in pushing fertilizer is that you "grow beautiful green cabbages" that do not bloom!!!

I consult a garden center person for their opinion. I will always decide what is best for my plants.

I don't fertilize crepes at all. Water, and lots of it, is all I give them when young. And brother, do they ever respond to water in a visible way. Crepes are very tolerant trees. Whether there is a drought, or they succumb to the dreaded powdery mildew in rainy spells (if treated). Crepes will just lose CURRENT foliage/blooms and come back later that season (or the next). Crepe's are 'survivors', inother words. That's why the TX Highway Department plants them in the medians: they will grow in crappy soil; they can live with very little water (once they're 2' tall) and they need zero care.

TIP: Plant them with lots of space around each tree, as they grow broad and need air circulation to dry leaves after rain. If you do this, they will rarely even get powdery mildew (which crepes are prone to because of poor planting practices). Crowding several close together is done because people think they need to do this for big IMPACT, but this is a big mistake, as it prevents needed air circulation. You don't want water sitting on the foliage too long, resulting in powdery mildew. At the first sign of the white, powdery appearance on leaves, spray with water mixed with a little detergent of dish soap. It kills the grayish mildew.

Crape Myrtles are not heavy feeders like roses are but they may benefit from a single, slow release, application in Spring if you want to feed them. They can feed off decomposing mulch if you mulch them. They may also benefit from regular fertilizer applications if your soil has nutrient deficiencies, as happens with some sandy soils.

When it doesn't rain a lot here, the crapes stop blooming.