Good to hear crickets can be aggressive. Well I wouldn't think that shed be stressed from not having coverings then. Do you have each frog in the same tank with dividers? If so you need a temp gauge in each frogs area. I know you said you believe the humidity is correct but I'm seriously reccomending you purchase hygrometers and place them in each frogs area. Humidity drops very quickly and you can't know for sure if its correct if you have no way to measure its accumluation within the tank. Humidity also affects growth/activity/appetite/hydration/and ease of shedding. It is a must for these tropical frogs. Just because the substrate is moist doesn't mean that the air within the enclosure is moist enough. Moisture in the air helps them keep hydrated. I don't want to be pushy, but assuming that its right doesn't make it so. I'm just trying to help. I don't want you to feel offended.