I was busy today and asked my brother to feed my beardie (which i’ve had around 3 weeks). When I got home I asked him how it went and long story short he fed my beardie 2 dead, small crickets. I know you shouldn’t feed dead crickets to a beardie but should i be worried that he could have a parasite or something? what are some signs that i should watch out for in the next few days?
I wouldn't worry much. All feeders, live or dead , can carry parasites. Of course it's not a good idea to feed them dead bugs but it shouldn't do anything that will cause your dragon to act ill. How big is your beardie + how long have you had him ? At some point a fecal check can be a good idea but usually when they are past the very small baby stage so the meds. don't affect them too badly.
I wouldn't risk it. They could have died because of parasites or being sick. You don't want that passed onto your bearded dragon. Stay safe and get fresh crickets.