I have been using Elimi-phos rapid and had to go twice the recommended rate.
Then I went twice the rate twice a day.
Then it started doing something.
And I am dosing 400 gallons (1500liters) SO I am hitting it with 25-30ml at a time.
You are dosing the amount it says to drop it by 0.1
Double it and do it 2 or 3 times a day. The great danger is hitting zero and you dont have to worry about that yet.
Even it it is only 1 your are safe. Keep testing.
Does your skimmer have a lid with holes? Run a piece of air line tubing down into the skimmer but not to the bottom. Just about half way. Fold the tubing back and put a twist tie on it loosly.
This will allow you to create a fast drip you control with the pinch where the tube is bent back. Put the Lanthanum in some RODI and siphon it into the slimmer slowly. I just sit a plastic measuring cup on the skimmer lid. Fill it with RO/DI water and add the LaCL.
I just switched to PhosBan-L on a doser. The doser pumps it into the skimmer on a schedule.
PhosBan-L is 4 times stronger than what you are using so you use less.