Looks hungry, are you fertilizing them?

I gave it fish emulsification the other day is there something else I should give it?

I don't use fish emulsion, so I don't know what's in it, but watermelons are heavy feeders. I give my container watermelons some granular fertilizer a couple of times a season (early and mid) heavy on the phosphorus, and I use a balanced liquid fertilizer at 1/4 strength at every watering. watermelons need the P (phosphorus) for roots, flowering, and fruiting.

Oftentimes the center cluster of the oldest leaves may fade and yellow after a while. As long as that doesn't spread beyond the first few leaves, you are likely to go.