Upper body too weak for deadlifts?

Hey everyone!

Glad to be back in the community after months of not working out (too busy due to work)... I'm back on the exercise train and here to stay:)

Today I did Kelli's just squats and deadlifts routine, which was fun but difficult. While doing the deadlifts, however, often I'd have to drop my weight because my forearms and wrists would get too tired to hold my weights. Same was true for some of the squat intervals - my forearms and wrists would tighten up and I'd have to drop my weights before my legs got tired.

Unfortunately this has been preventing me from upping my weight for the lower body, which is stronger than my upper body. As part of FB 30 I've been working my upper body consistently but it still isnt strong enough to hold more than 20lb each hand for the deadlifts.

I'd appreciate any advice, thank you!!