Only using Big Bloom until now

Since the start of my grow the only nutrients I have been using is the FF Big Bloom. Last night I switched them over to flower. I have a feeling the nutrients are lacking because some of the lower leaves are starting to get spots of yellow on them. A couple that are way underneath on the bottom have turned completely yellow and are droopy. They aren't curling up at all but they are getting yellow spots. And it's only the very first set of leaves. All of the new growth looks great. Should I go and pick up the the Tiger Bloom and start with that now that I've switched them to flower?

I know what the feeding schedule says, but I just wanted some real world opinions from more advanced growers.

Thanks.