And no idea how long ago they could have eaten this?
If it is possible that it has been within the past few hours, I would go ahead and try to induce vomiting in them unless they have a medical condition that would make this inadvisable (such as megaesophagus or laryngeal paralysis).
For the 30 pound dog, I would give between 20 and 30 ml of hydrogen peroxide orally. For the 65 pound dog I would give 45 ml of hydrogen peroxide.
Luckily, based on my calculations, according to the ASPCA toxicology center, your dogs could have ingested a total of 600 mg of elemental iron (up to 25 tablets of 65 mg size of anhydrous ferrous sulfate, which is only 37% elemental iron, so 37% of 1625 mg would be a total of about 600 mg of elemental iron). If one dog ate ALL the tablets alone, for your larger dog he would have received about a 20mg per kg of body weight dose. For the smaller dog, a 46 mg per kg of body weight dose. Symptoms are not usually seen at doses less than 20mg per kg, so the larger dog would likely have no symptoms. At doses between 20 and 60 mg per kg we can see milder clinical signs (GI upset- vomiting, diarrhea, anorexia). At doses higher than 60mg per kg more severe signs can arise. So luckily, if any signs develop, we should just have mild GI upset, but inducing vomiting may be prudent just to be on the safe side!!!