It's been a week since I switched to flowerin...

Sometimes the new growth is slightly light green but this looks like the start of a sulfur deficiency. If you have some red/purple streaks or strips running up your main stems that's a sure sign. Also the stems start getting hard or woody. It can happen if your ph is too high or your substrate ph is too high. Ideally in soil a ph between 5.8 to 6.5 is an acceptable range. You should check the ph of your runoff coming out of the pot to give you an idea of whats going on inside the pot. If what your putting in and coming out are in range you can supplement the deficiency with plain Epsom salt (Magnesium Sulfate) at 1 teaspoon per gallon of water. You should see improvement in 3-4 days. If not you can take an additional step and use the same mix as a foliage spray a couple of times a week. Be sure to get under the leaves where the stoma are located also. Try to do it at lights out so your lights don't magnify the water droplets and leave marks on your leaves. Good luck you'll be seeing green in no time.