brewerm yeast no activity

I have been brewing for about 2 years and decided to try a lager. We made 3 5 gallon batches and used brewferm lager yeast in all three. I pitched I made a yeast starter with dme first thing inthe morning and pitched the yeast into it and let stand at about 70 degrees for about 5 hours until the wort was ready to pitch the yeast into it. I then put the wort into my fermentation chamber at 50 degrees and it has been in there for four days and there is no activity. I have no experience with lagers. Any help from the vast experience on this forum would be greatly appreciated.

 

The only "activity" that means anything is numbers on a hydromter. If you want to know what's going on, take a gravity reading.

 

I took a gravity reading on the third day and it hasn't changed. On the fourth day I gave each one a little shake and this morning the fifth day I am starting to see a little activity on two of the three batches. Tomorrow I am planning on taking another reading to see if they are changing.

This is my first attempt at lagers and I want to know if this is normal.