No, it's a participle. "Being used as adjectives" is a participial phrase being used as an adjective, to coin a phrase, and modifying "present participles". The second one is also a participle being used as an adjective, but this time it's a past participle rather than a present one. Neither is a gerund, which looks like a present participle in form, but has a different function, that of a noun: e.g. "Swimming is good for the health".