Lack of blooms may be due to a lack of good light or possible a combination of stresses such as moisture or lack of nutrition.
Yellowing of inner leaves can be due to a number of things. There is a natural loss of older leaves periodically especially as new growth emerges or as the plant is in a major bloom cycle. Dry soil or soggy soil conditions for a period of time may also be involved in yellowing and drop of older leaves. Finally if the bush is just not that green overall and older leaves are yellowing, a lack of nitrogen could be to blame.
It may be a magnesium deficiency. One way to tell is to mix two tablespoons of Epsom salts in a gallon of water and drench the area beneath the branch spread of the plants. If they green up in a week or two, that is your cue.
If not you may want to have a soil test done to see what the various nutrient levels are.
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