Exodus 7:22 DRB:
And the magicians of the Egyptians with their enchantments did in like manner: and Pharao's heart was hardened, neither did he hear them, as the Lord had commanded.
Exodus 8:7 DRB:
And the magicians also by their enchantments did in like manner, and the brought forth frogs upon all the land of Egypt
Exodus 8:18 DRB:
And the magicians with their enchantments practiced in like manner, to bring forth sciniphs, and they could not and there were sciniphs as well on men as on beasts.
The Egyptian Magicians in Exodus 7:22; 8:7, as it seems, did miracles like that of Moses, while in Exodus 8:18 they were trying to antagonize the effect of Moses' miracle.
Why in Exodus 7:22; Exodus 8:7 they did not try to antagonize the effect of Moses' miracles?