BUGGYCRAZY said:My Guess - Hot soil, dry soil, or pH too high. Try some acidifying fertilizer if you think it could be pH. Try double potting (putting the pot into a larger pot to shade it) if you think it is too hot. It really doesn't look like wet soil, more like it is suffering nutrients, maybe a bigger pot? they like lots of room for their bulbs. and they like acid soil.
BUGGYCRAZY said:If you do not want to add fertilizer (in case you already have some in there) you can try using just sulfur, it acidify the soil, just a little at a time (2Tablespoons in 1 gal -you can google the conversion) and see if color improves. You can also try Epsom salts, magnesium deficiency can cause yellowing, it won't hurt to try.
My orientals in the sun look like that, then get worse but as much I I try I just can't change the weather here - it is a VERY bad year.