I have an 18 month old Mastiff (who just brought me his favorite toy becasue I am not playing with him before I go to the office
). Here is his weight progression 5 months through 9 months. He now is a little over 200 but is thin (I know that sounds funny). He could be 230 but I tr to keep him as lean as possible to mimize unnessary wear and tear. AS long as you pup is active and happy I would not get too concerned about weight. With a Mastiff it is a journey not a weekend trip and it can take up to 24+ months for full maturation.
5 Months
28-May 76.7
19-Jun 92
6 Months
24-Jun 96.5
28-Jun 98.5
3-Jul 106
14-Jul 106.5
7 Months
26-Jul 116
5-Aug 119.6
12-Aug 122.2
8 Months
24-Aug 130.6
9-Sep 133.3
9 Months
24-Sep 142.2
14-Oct 155